Answer
Please see the work below.
Work Step by Step
We know that
a.$ \frac{200.6g\space Hg}{1mol\space Hg}\times \frac{1mol\space Hg}{6.022\times 10^{23}Hg\space atoms}=3.331\times 10^{-21}\frac{g}{Hg\space Hg\space atom}$
b. $\frac{20.18g\space Ne}{1mol\space Ne}\times \frac{1mol\space Ne }{6.022\times 10^{23}Ne\space atoms}=3.351\times 10^{-23}\frac{g}{Ne}$
